For me, when considering large item purchases (fishing gear or otherwise), I tend to first look at versatility-how much use in different situations or applications can I get. Couple examples, for my first rod I picked up a 6wt, seems to do pretty well throwing anything from small dry's to decent size poppers and bass bugs; for an EDC sidearm I go with Rugers .357 LCR, able to shoot magnum loads plus .38spc and .38+P, kinda like having three pistols in one.
Quality is right next if not tied for first, how well is something constructed, how long will I be able to use it, will it hold up with minimal required maintenance or work.
Finally pricing is my other big focus. If I'm happy with the first two consideration points, I'm usually willing to pay a bit more (within reason). Of course it's really hard to pass up a great deal when you find one and sometimes logic just has to take a backseat.